js 普通数组对象转树形（Tree）图数据结构

let obj = [
    {id:1,pid:0},
    {id:2,pid:0},
    {id:3,pid:1},
    {id:4,pid:2},
    {id:5,pid:3},
]
function formatterData(arr,pid) {
    return  arr.filter(item=>item.pid==pid).map(item=>({...item,children:formatterData(arr,item.id)}))
}
function arrayToTree (items) {
    const result = [];   // 存放结果集
    const itemMap = {};  // 
    for (const item of items) {
        const id = item.id;
        const pid = item.pid;

        if (!itemMap[id]) {
            itemMap[id] = {
                children: [],
            }
        }

        itemMap[id] = {
            ...item,
            children: itemMap[id]['children']
        }

        const treeItem = itemMap[id];

        if (pid === 0) {
            result.push(treeItem);
        } else {
            if (!itemMap[pid]) {
                itemMap[pid] = {
                    children: [],
                }
            }
            itemMap[pid].children.push(treeItem)
        }

    }
    return result;
}
console.log(arrayToTree(obj))
console.log(formatterData(obj,0))